1. Field of the Invention
The invention relates to a seat cushion, in particular for an aircraft seat, of the type comprising a supporting body of a framed plastic having a spring core embedded therein and a flameproofing layer of flame-retardant plastic foam to which a covering material is connected, preferably detachably.
2. Description of the Prior Art
A known seat with a cushion of foamed plastic--described for example in published PCT application WO-87/06894 application of C. A. Greiner & Sohne GmbH--comprises a foamed plastic with a support body of an open-celled, resilient plastic foam having a first density and a flameproof layer of an open-celled resilient foamed plastic, provided with a flameproofing agent, having a second density which is different from said first density. The plastic foam and the flameproof layer are connected with each other, in particular through a foaming process, and are surrounded by a flame-resistant covering material. In order to achieve a sufficient permeability to air on the part of such a cushion, it has also been proposed, after the completion of the cushion, to push heated needles through, so that a corresponding exchange of air is possible. These cushions have proved to be very successful in practice; however, it has been found that, especially in extreme weather conditions, or under various climatic conditions, the sitting comfort of the seats for the planned usage in vehicles was not sufficient.
In addition, seats for public transport are also known --as disclosed in German Utility model 85 06 816--which have a seat cushion, which is covered with a seat cover, in which the seat cover and the seat cushion consist of a flame-resistant and low-smoking material. Between the flame-resistant seat cover and the seat cushion, mostly consisting of plastic foam, there is often arranged a glass fibre mat which is intended to prevent the seat cover from burning through in the direction of the seat cushion. However, it has been found here that in many cases, the action of the flames arises from the direction of the floor and the plastic foam of the seat cushion tends to burn, with an intensive generation of smoke, whereby in the case of fire, the vehicle is so full of smoke in the shortest period of time that it is scarcely possible for the occupants to find their bearings. Accordingly, in the case of this known seat, provision is made that beneath the seat cushion in the supporting frame of the seat, a fire-resistant plate is arranged. This requires the use of a special section for mounting the seat padding and also requires an additional expenditure through the arrangement of the fire-resistant plate. In this embodiment, the ventilation of the seat was not satisfactory, either.
Seats with cushions of foam plastic are very widely used in modern vehicle construction. They are used above all in rail and road vehicles, but also to a predominant extent in aircraft. Whilst the regulations applicable to rail vehicles with regard to the self-extinguishing construction of the materials which are used, or respectively the generation of smoke, prescribe very strict guiding principles, the regulations applicable in the aircraft industry are even more stringent. Thus, a test is prescribed in the case of seats permitted for use in aircraft, in which the cushions, in their composition as provided for installation, are directly exposed to a flame from a burner. This flame acts over a period of 2 minutes directly onto the cushion, after which the flame is extinguished or removed. The cushion is extinguished after 5 minutes, if the flames have not extinguished themselves by that time. After this fire test, the weight loss of the cushion must not be higher than 10%. In order to fulfil these extremely strict regulations, and at the same time also achieve a high degree of sitting comfort in the seats in the case of flights of long duration and to achieve a low weight, seat cushions of various open-celled, elastic soft foam plastics, provided with flameproofing agent and having differing densities, are stuck together.
Such a known vehicle seat--as described in European specification A1 190 064--comprises several layers of needle fleece, which are surrounded by a flameproof covering material. Between the covering material and the individual layers of needle fleece, to reduce damage by vandals, reinforcement mats of metal or glass fibres are arranged. Through the sticking of the individual layers and the many intermediate layers of this vandal-proof layer, sufficient ventilation is still difficult to achieve in the known vehicle seat.
In another known seat for aircraft, in order to produce the complicated three-dimensional fashioning of the seat cushions more simply, the supporting body is formed from a part which is foamed in one piece in a mould and is mixed with flameproofing agents, the surface of which is covered with a flameproofing layer and thereafter with a flameproof covering material. With the known seats, however, the new increased safety specifications and testing regulations for aircraft seats could not be fulfilled.